Method and apparatus for treating recording media to enhance print quality in an ink jet printer

ABSTRACT

Plain paper is processed through a plain paper optimizer system prior to image formation on a recording surface. The optimizer system adds a fixing fluid during application of pressure and, optionally, heat to the paper surface. The surface contacted by the fixing fluid is enhanced, forming images of improved print quality. In one embodiment, plain paper is treated in an optimizer system, which has a heat and fuser assembly with silicone oil as the fixing fluid, and is transported into the print zone of an ink jet printer. Images printed on the treated surface demonstrate improvements in image quality manifested by reduction of both edge raggedness and intercolor bleeding.

BACKGROUND OF THE INVENTION AND MATERIAL DISCLOSURE STATEMENT

The present invention relates generally to printers which deposit markson a recording medium to form images thereon and, more particularly, toa pre-print treatment of the recording media to enhance the printquality of the printed image.

Ink jet printers of the so-called “drop-on-demand” type have at leastone printhead from which droplets of ink are directed towards arecording medium. Within the printhead, the ink is contained in aplurality of channels and energy pulses are applied to transducers tocause the droplets of ink to be expelled, as required, from nozzles atthe ends of the channels.

In a thermal ink jet printer, the energy pulses are usually produced byresistors, which are individually addressable by current pulses to heatand vaporize ink in a channel or recess proximate to the nozzle. As avapor bubble grows, ink bulges from the nozzles until the current pulsehas ceased and the bubble begins to collapse. At that stage, the inkwithin the channel or recess retracts and separates from the bulging inkwhich forms a droplet moving in a direction away from the nozzles andtowards the recording medium. The channel or recess is then re-filled bycapillary action, which in turn draws ink from a supply cartridge.Operation of a thermal ink jet printer wherein the ink is expelled fromchannels is described in, for example, U.S. Pat. Nos. 4,638,337 and4,774,530, which disclose a printer of the carriage type having aplurality of printheads, each with its own ink supply reservoir, mountedon a reciprocating carriage. The nozzles of each printhead are alignedperpendicular to the line of movement of the carriage and a swath ofimage information is printed on the stationary recording medium as thecarriage is moved in one direction. The recording medium is thenstepped, perpendicular to the line of carriage movement, by a distanceequal to the width of the printed swath and the carriage is then movedin the reverse direction to print another swath of information.

Many forms of recording media are known in the art. Special forms ofcoated paper are used to provide enhanced optical density andwaterfastness. See, for example, U.S. Pat. No. 5,457,486 and thereferences summarized in columns 1-3. The various coated paperconfigurations add expense to the printing process, and the greatmajority of output prints are produced on non-coated plain paper.Because of the low cost of paper, it is widely used in spite of severalproblems with the quality of images printed thereon. Because the imagesare formed of aqueous based ink droplets falling onto an absorbentsubstrate, problems are created such as raggedness along the edges ofthe image; intercolor bleed (when printing more than one color), line“blooming”, optical density and image permanence.

It has been appreciated that application of heat to plain paper, eitherbefore, during or after the printing, helps to alleviate some of theabove-identified problems. U.S. Pat. No. 5,428,384 discloses use of apreheated drive roller to drive some moisture out of the paper andelevate the paper temperature to reduce paper cockle and curl. Apost-heat blower dries the ink rapidly after being deposited on therecording media to help reduce smearing.

U.S. Ser. No. 08/523,322 filed on Aug. 30, 1995 and assigned to the sameassignee as the present invention, utilizes a segmented flexible heaterto pre-condition the record medium prior to entering the print zone.U.S. Pat. No. 5,380,769 discloses forming an ink image on a substrate;applying a release agent to the image and transferring the image to arecording medium at a fusing station.

Copending application U.S. Ser. No. 09/069,111 assigned to the sameassignee as the present invention, filed concurrently herewith, with thenamed inventors Thomas W. Smith, Samuel Kaplan, Kathleen M. McGrane, andDavid J. Luca, the disclosure of which is totally incorporated herein byreference, disclose a process which comprises (a) applying to asubstrate a fixing fluid which comprises a material selected from thegroup consisting of (1) block or graft copolymers of dialkylsiloxanesand polar, hydrophilic monomers capable of interacting with an inkcolorant to cause the colorant to become complexed, laked, or mordanted,(2) organopolysiloxane copolymers having functional side groups capableof interacting with an ink colorant to cause the colorant to becomecomplexed, laked, or mordanted, (3) perfluorinated polyalkoxy polymers,(4) perfluoroalkyl surfactants having thereon at least one group capableof interacting with an ink colorant to cause the colorant to becomecomplexed, laked, or mordanted, and (5) mixtures thereof; (b)incorporating into an ink jet printing apparatus an ink compositionwhich comprises water and a colorant which becomes complexed, laked, ormordanted upon contacting the fixing fluid; and (c) causing droplets ofthe ink composition to be ejected in an imagewise pattern onto thesubstrate.

Copending application U.S. Ser. No. 09/069,110 assigned to the sameassignee as the present invention, filed concurrently herewith, with thenamed inventors Thomas W. Smith, John S. Facci, Michael J. Levy, andDavid J. Luca, the disclosure of which is totally incorporated herein byreference, discloses a fluid deposition apparatus comprising (a) a fluidsupply, (b) a porous fluid distribution member in operative connectionwith the fluid supply, enabling wetting of the fluid distribution memberwith a fluid, and (c) a porous metering membrane situated on the fluiddistribution member, whereby the metering membrane enables uniformmetering of the fluid from the fluid distribution member onto asubstrate.

SUMMARY OF THE INVENTION

It would be desirable to improve the print quality of a plain papermedia by a simple pre-print treatment of the paper. The presentinvention provides a pre-print treatment which includes moving thepaper, prior to recording thereon, through a plain paper optimizersystem which includes at least pressure treatment of the paper coupledwith application of a fixing fluid such as silicone oil to the papersurface. In a described embodiment, the optimizer system is a rollerfuser system which fuses toner images transferred to plain paper. Theplain paper emerges from the optimizer system with a uniform thincoating of the fixing fluid on the recording surface. The treated paperis subsequently printed on to form an output image, which has enhancedprint quality with improvement in intercolor bleed and edge raggedness.

More particularly, the present invention relates to a method forprinting images with improved print quality onto a treated plain paper,comprising the steps of:

moving plain paper from a paper supply into a plain paper optimizersystem,

subjecting the paper to at least a pressure force while applying afixing fluid onto the paper recording surface, resulting in a treatedpaper,

moving the treated paper into a print station,

applying a marking material in image configuration onto said treatedpaper recording surface and

moving the paper into an output station.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the basic elements of areciprocating carriage type of thermal ink jet printer incorporating thepaper optmizer system of the present invention.

FIG. 2 is a schematic block diagram showing the basic concept of asystem for treating plain paper to enhance the quality of prints formedon a recording surface.

FIG. 3 is a block diagram of a hybrid copier/printer system whichutilizes an optimizer system to fuse developed transfer images formed bythe copier and uses the same optimizer system to pre-treat paper to berecorded on in an ink printer.

DESCRIPTION OF THE INVENTION

FIG. 1 shows a reciprocating carriage-type thermal ink jet printer 8 forcreating color or monochrome images on a pre-treated sheet 9. Printer 8is exemplary only. Other types of ink marking devices, such aspiezoelectric ink jet, acoustic ink jet or a multifunction printer canbe used. An ink cartridge 10, having a plurality of ink suppliestherein, is preferably removably mounted on a carriage 12. This carriage12 is adapted to move in a back-and-forth manner in direction C acrosssheet 9, which is moving in a process direction P. The sheet 9 is fedfrom a paper supply 25 by conventional feeding means along a paper pathand in direction P by means of a stepper motor or other indexing motor13, which is preferably adapted to cause the motion of sheet 9 indirection P in a stepwise fashion, holding the sheet 9 in a stationaryposition while the cartridge 10 moves across the sheet in direction C,and then indexing the sheet 9 in processing direction P between swathsof printing caused by the action of cartridge 10 being carried oncarriage 12.

Carriage 12 is provided with one of various possible means for movingthe cartridge 10 back and forth across sheet 9. As shown in FIG. 1,there is provided a rotatable lead screw 14 having threads thereon whichinteract with a structure on the carriage 12 so that, when lead screw 14is caused to rotate by a motor (not shown, the interaction of the leadscrew threads with the structure on carriage 12 will cause the carriage12 and the cartridge 10 mounted thereon to move in direction C acrossthe sheet 9. Preferably, in most embodiments of an ink jet printer foruse with the present invention, the carriage should be controlled toallow substantially even back-and-forth motion of the cartridge 10 sothat the printing operation can be carried out in both directions. Thismay be accomplished, for example, by operatively attaching lead screw 14to a bi-directional motor, or providing oppositely-wound sets of leadscrew threads on lead screw 14 so that, once carriage 12 is moved to oneside of the sheet 9, the structure on carriage 12 will re-engage withthe opposite-wound threads on lead screw 14 to be moved in the oppositedirection while the lead screw 14 is rotated in the same rotationaldirection.

Attached to cartridge 10, as shown in FIG. 1, is a printhead 20, whichis shown directed downward toward the sheet 9. Printhead 20 comprisesone or more linear arrays of thermal ink jet ejectors, each ejectorbeing operatively connected to a particular ink supply. Generally, thelinear array of ejectors in printhead 20 extends in a direction parallelto process direction P, so that, when the cartridge 10 is caused to movein carriage direction C, the linear array will “sweep” across the sheet9 for an appreciable length, thus creating print swaths. While thecarriage is moving across the sheet 9, the various ejectors in thelinear array are operated to emit controlled quantities of ink ofpreselected colors in an image-wise fashion, thus creating the desiredimage on the sheet. Typical resolution of the ink jet ejectors inprinthead 20 may be from 50 spots per inch to 1200 spots per inch.

Also provided “upstream” of printhead 20 is a paper optimizing systemwhich, in one embodiment, is a heat and pressure fuser system 30. System30 includes a heated roll 32 and a roll 34 to which a loading force F isapplied by conventional means at nip 36. The leading edge of sheet 9enters into nip 36 and is moved in direction P in combination with themovement provided by motor 13. The fuser assembly further includes asump 38 containing a fixing fluid and a meter roll 40 for transferringthe fixing fluid from sump 38 to roll 32.

Operatively associated with the printer 8 is a controller 31. Controller31 coordinates the “firing” of the various ejectors in the printhead 20with the motion of cartridge 10 in carriage direction C, and with theprocess direction P of sheet 9, so that a desired image in accordancewith the digital input image data is rendered in ink on the sheet 9.Image data in digital form is entered into controller 31, and controller31 coordinates the position of the printhead 20 relative to sheet 9 toactivate the various ejectors as needed, in a manner generally familiarto one skilled in the art of ink jet printing. Controller 31 will alsocontrol operation of motor 13, fuser 30 and paper supply 25. Furtherdetails of the operation of a printer corresponding to printer 8 arefound in U.S. Pat. No. 5,455,610, whose contents are hereby incorporatedby reference.

As sheet 9 proceeds through the fuser assembly 30, it acquires auniform, thin layer of the fixing fluid. As the sheet advances into theprint zone, ink is projected from printhead 20 creating an imageconsisting of a plurality of print swaths. When the print operation iscomplete, sheet 9 is deposited in an output station (not shown),typically an output tray.

It has been found that, because of the fuser pre-treatment, the qualityof the output print has been improved. The image quality parameters ofedge raggedness and color interbreed were evaluated and compared withprint quality of untreated plain paper. The results are summarizedbelow.

EDGE RAGGEDNESS IMPROVEMENT

Table I shows the results of the measurements performed on treated anduntreated paper to verify improvements in edge raggedness. The fusersystem 30 used was that contained in a commercially available Xerox 5100Copier which uses Dow Corning 200 fluid as the fixing fluid. A fuserlamp heater at the measured power consumption of approximately 1400watts (for fusing 11 inch paper). The average pressure in the nip is0.5958 N/mm² (N=Newton), and the calculated average nip dwell time isapproximately 29.67 ms. A uniform layer was formed on an 8½×11 inchrecording sheet with a thickness of 1-5 micro-liters.

The print mechanism was a commercially available HP 850C ink jetprinter.

TABLE I Top MFLEN Bottom MFLEN Experiment #1 Lab Exposure untreated 4.7710.68 treated 0.13 2.47 treated overnight 1.13 3.70 Experiment #2 LabExposure untreated 1.83 4.03 treated 0.40 1.23 70% RH untreated 2.8312.37 Exposure treated 0.53 1.53

Edge raggedness is measured by a standardized process which reports aMid Frequency Line Edge Noise (MFLEN) value. For a black line printed ona yellow background, an automated measuring device records a MFLEN valuealong the top and bottom of a printed line. An average of the top andbottom MFLEN values are usually reported, however, due to an apparentsystematic jet directionality error in the particular HP 850C printheadused for these experiments, both numbers are reported.

The first test conducted involved preparing two treated papers. One wasprinted immediately after fusing and the second was allowed to setovernight and printed the following day. This experiment was done todifferentiate the effects of heat and oil treatment to which the paperis exposed in a xerographic fuser subsystem. As described supra, it iswell known that preheating the paper drives out moisture and improvesintercolor bleed and edge raggedness. The data in Table I clearlydemonstrates a dramatic MFLEN improvement of the treated papers to theuntreated. A slight degradation is observed for the paper that satovernight before printing which is consistent with a reduction in paperwater content due to heating in the fuser. To further explore the effectof moisture, a second experiment was done in which two treated sampleswere prepared. One paper was allowed to sit overnight in a 70% RHenvironment with an untreated paper. An equivalent set was allowed tosit overnight in laboratory conditions. Print samples were produced thenext day immediately after the papers were removed from the humidityenvironment. The results, reported in Table I, again show a dramaticimprovement in edge raggedness for treated papers. There is nodiscernible effect of humidity on the treated papers, whereas for theuntreated papers the effect of humidity is quite apparent.

INTERCOLOR BLEED REDUCTION

Table II shows the improvement in intercolor bleed when paper ispre-treated. The intercolor bleed value average expresses MFLEN valuesfor the line edges when one color is printed next to the other. Papersamples were treated by running through the same 5100 fuser describedabove. The samples to be treated and untreated were placed in a humiditychamber and humidified to RH 70 in order to eliminate the effect ofpaper dryness and heat. The printer used is a multi-die, color printheadwith 600 dpi resolution and ejecting a carbon-based ink. Three differentintercolor bleeds were considered: black/color; primary color/primarycolor and primary color/secondary color. All these combinations weresignificantly improved by this pre-treatment process; for yellow/black,from 4.2 to 1.2; for cyan/yellow, from 23.6 to 15.1 and forgreen/yellow, from 28.1 to 17.05.

TABLE II Untreated Fuser Treated Ink Combination top bottom top bottomYellow-Black: 1 5.8 0 0.6 0 2 4.9 0 2.8 0 3 11 3.9 4 0 average 7.2333331.3 2.466667 0 average 4.266667 1.233333 Cyan-Yellow: 1 18.6 33.4 15.312.2 2 22.9 21.3 21.5 16.1 3 27.2 18.4 9.3 16.3 average 22.9 24.3666715.36667 14.86667 average 23.63333 15.11667 Green-Yellow: 1 37.2 32.321.5 20.5 2 23.2 23.1 12.9 22.1 3 34.1 19.2 7.4 17.9 average 31.524.86667 13.93333 20.16667 average 28.18333 17.05

While the embodiment of FIG. 1 used a paper optimizer system whichincluded heat and pressure, it is believed that the primary enabler forobtaining improvements in edge raggedness and intercolor bleed reductionis the application of pressure to provide the thin fixing fluid coating.Therefore, as an alternate embodiment, roll 32 could be an unheatedroll.

From the above description, it will be appreciated that the paper can bepre-treated without immediately being moved into a print station. FIG. 2shows a simplified block diagram showing paper fed from a paper supply50 into plain paper optimizer 52 which can have the characteristics ofthe fuser 30 described supra. The paper acquires a treated surface andis collected at output tray 54. The treated paper can then be stored forsubsequent use or shipped to other locations.

FIG. 3 shows a copy/print system 60 which enables either copying animage to produce a black and white copy or producing a color copy in acolor marking device. A fuser, which can be incorporated into the copieror can be used as a stand alone device, is commonly used for eithercopying or a printing function. Referring to FIG. 3, system 60 includespaper from supply 62 fed into either a copier 64 or directly into apaper optimizing system 66 under controller of a controller 68. System66, in a preferred embodiment, is the fuser system disclosed in FIG. 1.System 66 can be a stand alone unit, as shown, or can be incorporatedinto copier 64. Copier 64 has the conventional xerographic stationsincluding an optical imaging station for forming an image on aphotoreceptor, a station for developing the image and a station fortransferring the image to a sheet of paper from supply 62. An exemplarycopier is disclosed in U.S. Pat. No. 4,081,213, whose contents arehereby incorporated by reference. If system 60 is being used to produceblack and white copies, a process sheet with the developed imagetransferred to a surface, is moved into system 66, where heat andpressure are applied simultaneously with application of a fixing fluidas described supra. The sheet bearing the fused image is deposited at anoutput station 70. If system 60 is being used to produce a color print,a sheet from supply 62 is moved directly into system 66 wherein thesheets recording surface is treated and then moved into the colorprinter marking station 72. Color images are formed on the treatedsurface, and the color print is deposited in the output station.

While specific characteristics have been provided for a heat andpressure system, it will be appreciated that the requirements fortreating paper to improve the image quality may differ from thecharacteristics of the fuser used as the paper optimizer in the aboveembodiment. For example, a different pressure and/or heating range maybe preferred for certain systems.

While the embodiment disclosed herein is preferred, it will beappreciated from this teaching that various alternative, modifications,variations or improvements therein may be made by those skilled in theart, which are intended to be encompassed by the following claims:

What is claimed is:
 1. A method for printing images with improved printquality onto a treated plain paper, comprising the steps of: movingplain paper from a paper supply into a plain paper optimizer system,subjecting the paper to at least a pressure force while applying afixing fluid onto the paper recording surface, resulting in a treatedpaper, moving the treated paper into a print station, applying a markingmaterial in image configuration onto said treated paper recordingsurface, moving the paper into an output station, and applying heat tosaid paper during the step of subjecting the paper to pressure.
 2. Anink jet printer comprising: a paper supply, a plain paper optimizerstation, means for moving a sheet of plain paper from said paper supplyinto said optimizer station, means for applying at least a pressureforce at said optimizer station to said paper while applying a fixingfluid to a recording surface of the paper to form a treated sheet, aprinter for placing marks on said treated sheet in an imageconfiguration, means for moving the treated sheet into a marking stationof said printer and forming an image thereon, means for moving the sheetfrom said printer marking station to an output station, and means forapplying heat to said paper simultaneously with application of saidpressure force.
 3. A recording apparatus for forming images on a plainpaper recording medium, including: a paper supply, a black and whiteelectrophotographic reproduction machine including an optical stationfor forming a latent image on a photosensitive image member, means fordeveloping said latent image, means for transferring said developedimage to a sheet of paper fed from said paper supply, a color inkjetprinter, control means for selectively moving a sheet of paper from saidpaper supply to either said optical station of said reproduction machineor to a fuser station, said fuser station comprising means for applyingat least a pressure force to said sheet of paper while applying a fixingfluid to a recording surface of the sheet of paper, said control meansfurther selectively moving a treated sheet with a developed fixed imageto an output station or a fused sheet without images into said colorinput printer to form a color image on said treated sheet and means formoving the color print into said output station.